Sensor methods and devices for quantification of volatile and nonvolatile compounds in fluids are known in the art. Typically, quantification of these parameters is performed using dedicated sensor systems that are specifically designed for this purpose. These sensor systems operate using a variety of principles including electrochemical, optical, acoustic, and magnetic. For example, a variety of spectroscopic sensors operating with colorimetric liquid and solid reagents are available to perform evaluation of color change.
It is known that conventional CD/DVD (compact disk/digital video disk) drives can be used for conducting optical inspection of biological, chemical, and biochemical samples. However, in order to make these drives useful for detection of parameters not related to digital data stored on optical media, the optical system of the drives must be modified. For example, U.S. Pat. No. 5,892,577 describes an optical disk drive, which is modified to obtain the information related to chemical and biochemical detection. This modification included an addition of one or two more detectors that are used for transmission measurements. An original detector of the drive is used to read the digital address on the disk associated with the analyte-sensitive region. Added detectors operating in transmission mode provide information on the sample to be inspected. This information from additional detectors can be quantitative with 256 grey levels.
As the use of CD/DVD drives has developed, the development of sensors in conjunction with optical storage media has also developed for the use in CD/DVD drives. For operation of such a modified optical disk drive, special optical disks are prepared. For example, U.S. Pat. No. 6,327,031 discloses optical disks having a semi-reflective layer to reflect a portion of light to one detector and transmit a portion of light to another detector.
U.S. Pat. No. 6,342,349 describes another optical drive based measurement system. In this system, analyte-specific signal elements are disposed with the optical disk's tracking features. Thus, the analyte-specific signal elements are readable by the optics used for tracking, although modified or additional optics elements are added. For the system to be applicable, a signal responsive moiety is of a small size, compatible with the size of the focused light beam of the optical drive and is reflective. Most preferably, the signal response moiety is a gold microsphere with a diameter between one and three micrometers. The assay type used in this optical detection system is of a binary nature (see U.S. Pat. No. 6,342,349 column 15, lines 23-37) and is not easily emendable to quantitative analysis based on light absorbance, reflection, scatter, or other optical phenomena.
Another method has also been described to screen the recognition between small molecule ligands and biomolecules using a conventional CD player. A procedure was developed to attach ligands to the reading face of a CD by activating the terminus of polycarbonate, a common polymer composite, within the reading face of the CD. Displays were generated on the surface of a CD by printing tracks of ligands on the disk with an inkjet printer. Using this method, disks were created with entire assemblies of ligand molecules distributed into separate blocks. A molecular array was developed by assembling collections of these blocks to correlate with the CD-ROM-XA formatted data stored within the digital layer of the disk. Regions of the disk containing a given ligand or set of ligands were marked by a spatial position using the tracking and header information. Recognition between surface express ligands and biomolecules was screened by an error determination routine (see Org. Biomol. Chem., 1, 3244-3249 (2003)).
Different types of analyte-specific signal elements are also known in the art. International patent application WO 99/35499 describes the use of colloidal particles, microbeads, and the regions generated by a corrosive attack on one or several layers of a compact disk as a result of binding between the target molecule and its non-cleavable capture molecule. The analyte-specific signal elements can be arranged in arrays, for example, combinatorial arrays (International Patent Application WO 98/12559). In addition to the solid and gel types of analyte-specific signal elements, other types include the liquid-containing regions (Gamera Bioscience System, see: Anal. Chem. 71 4669-4678 (1999)).
In a related art, remote automated sensors have been employed for a variety of applications ranging from the cost-effective monitoring of industrial processes, to the determination of chemicals toxic to humans at locations of interest, to analysis of processes in difficult-to-access locations. For these and many other reasons, a wide variety of sensors have been reported that operate in the automatic, unattended mode. For example, sensors were reported that operate remotely for detection of toxic vapors, uranium ions, and many other species. Measurements have also been done remotely in space on manned and unmanned spacecraft.
Remote measurement systems can be initiated and monitored via the Internet where a dedicated sensor is connected to a computer that receives commands via the Internet as described in U.S. Pat. Nos. 5,931,913, 6,002,996, 6,182,497, 6,311,214, 6,332,193, 6,360,179, 6,405,135, and 6,422,061. Generally, upon receiving a command, the computer initiates a sensor that is specifically designed to perform a sensing function and is connected to the computer. The sensor performs the measurement, the computer receives the sensor signal, and optionally, sends the signal back to a control station.
Automated computer-controlled sensors for remote unattended operation known in the art have two distinct components. These components are (1) a sensor itself and (2) a computer. These components are designed and built to perform initially separate functions and further are combined into a remotely operated sensor system. The limitations of such approach include development of a sensor itself, and its adaptation for computer control.
In quantitative operation of a sensor, the accuracy of determinations often depends on the ability to provide an interference-free response. The interferences can arise from a variety of sources and can include chemical and environmental interferences. The ability to provide accurate data improves with the increase of the information content or dimensionality of the collected data per sensor region. Sensors or analytical instruments can be classified according to the type of data they provide as zero-, first-, second-, third- and higher dimension (or order) instruments. Such classification of analytical instruments is well accepted by those skilled in the art.
A measurement approach that generates a single data point per sensor region is a zero-order instrument. Such instrument generates a single data point which us a zero-order data array. A single number is a zero-order tensor known in mathematics.
First order measurement systems generate a string of multiple measurements across sensor region or per other parameter such as time, wavelength, etc. For example, first order (one-dimensional) measurements can be done across a sensor region to generate several data points across a cross-section of the sensor region. Other examples of first order (one-dimensional) measurements can be done over one sensor region as a function of wavelength or time.
Second order (two-dimensional) measurement systems generate two dimensions of multiple measurements per sensor region. For example, measurements can be done to image the whole sensor region to generate multiple data points in X and Y directions (or radial and angular distance) of the sensor region. Other examples of second order (two-dimensional) measurement systems can include measurements of multiple data points across one cross-section of sensor region as a function of another spatial direction, or wavelength, or time. Thus, second order measurement systems generate a matrix of an instrument response upon the change of two independent types of variables.
Third order (three-dimensional) measurement systems generate a matrix of an instrument response upon the change of three independent types of variables. In our example, three independent types of variables are two spatial coordinates that describe a sensor region and time. In this case, the sensor region is effectively imaged as a function of time. Thus, a response of the third-order system is a 2-D matrix of an instrument response upon the change of two independent types of variables which is further recorded when changed by the third independent variable.
Existing optical analysis techniques have not been entirely satisfactory for the measurement of multiple chemically sensing regions because, as mentioned above, the optical disk drive systems used by these methods often require costly and labor intensive modifications to carry out automated analysis of time critical samples.
Attempts have been made to design improved apparatus for rapid analysis of large numbers of test samples, but such analyzers are relatively expensive and usually require specialized detector instrumentation. Designing a relatively simple and cost effective system to analyze multiple samples has heretofore been difficult to achieve.
Thus, there exists a strong need for a simplified device that can easily be used to carry out optical analysis of multiple quantitative assays and/or other biological, chemical, and physical environmental parameters with high reproducibility.